libevent里event_* 函数使用了那种事件模型？

Question

知道libevent支持 select/poll/epoll时间模型。 今天突然想到 封装了libevent底层操作的 event_* 系列函数是使用了那种事件模型呢

Answer 1

<event.c>

#ifdef HAVE_EVENT_PORTS
extern const struct eventop evportops;
#endif
#ifdef HAVE_SELECT
extern const struct eventop selectops;
#endif
#ifdef HAVE_POLL
extern const struct eventop pollops;
#endif
#ifdef HAVE_EPOLL
extern const struct eventop epollops;
#endif
#ifdef HAVE_WORKING_KQUEUE
extern const struct eventop kqops;
#endif
#ifdef HAVE_DEVPOLL
extern const struct eventop devpollops;
#endif
#ifdef WIN32
extern const struct eventop win32ops;
#endif

/* In order of preference */
static const struct eventop *eventops[] = {
#ifdef HAVE_EVENT_PORTS
    &evportops,
#endif
#ifdef HAVE_WORKING_KQUEUE
    &kqops,
#endif
#ifdef HAVE_EPOLL
    &epollops,
#endif
#ifdef HAVE_DEVPOLL
    &devpollops,
#endif
#ifdef HAVE_POLL
    &pollops,
#endif
#ifdef HAVE_SELECT
    &selectops,
#endif
#ifdef WIN32
    &win32ops,
#endif
    NULL
};

按照上面的顺序，取第一个os支持的接口,如下初始化的过程：

<event.c>

struct event_base *
event_base_new(void)
{
...    
    base->evbase = NULL;
    for (i = 0; eventops[i] && !base->evbase; i++) {
        base->evsel = eventops[i];

        base->evbase = base->evsel->init(base);
    }

    if (base->evbase == NULL)
        event_errx(1, "%s: no event mechanism available", __func__);

    ...
}

下面是epoll的eventop封装

epoll.c

const struct eventop epollops = {
    "epoll",
    epoll_init,
    epoll_add,
    epoll_del,
    epoll_dispatch,
    epoll_dealloc,
    1 /* need reinit */
};